Kepler's Laws

Kepler's first law is: The orbit of every planet is an ellipse with the Sun at one of the two foci.

Kepler's second law states: A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.

Kepler's third law states that the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

An orbital maneuver is the use of propulsion systems to change the orbit of a spacecraft (the rest of the flight is called "coasting").

Natural satellites are celestial objects that orbit a larger body; artificial satellites are manmade objects put in the orbit of the Earth.